An organopolysiloxane compound having an unsaturated hydrocarbon onto the terminal silicon is useful as a base polymer of an addition curable silicone composition. The addition curable silicone composition forms a silicone gel or a silicone rubber each excellent in electric characteristics, cold resistance, etc., after curing, so that it has been utilized as a sealing agent, a filler or a coating agent of electric and electronic parts or a semiconductor device, and a photosemiconductor insulation-coating protective material, etc.
As a silicon compound having ethynyl groups at the both terminals, a low molecular weight monomer such as a low molecular weight silicon compound having ethynyl groups at the terminals, 1,3-diethynyl-1,1,3,3-tetramethyldisiloxane (CAS Registry Number: 4180-02-3), 1,5-diethynyl-1,1,3,3,5,5-hexamethyltrisiloxane (CAS Registry Number: 39490-70-5), 1,7-diethynyl-1,1,3,3,5,5,7,7-octamethyltetrasiloxane (CAS Registry Number: 40392-68-5), 1,9-diethynyl-1,1,3,3,5,5,7,7,9,9-decamethylpentasiloxane (CAS Registry Number: 40392-69-6) and 1,11-diethynyl-1,1,3,3,5,5,7,7,9,9,11,11-dodecamethylhexasiloxane (CAS Registry Number: 40392-70-9), etc., have been described, and there is disclosed a method for preparing an organopolysiloxane compound having an acetylene portion at the main chain which comprises subjecting these silicon compounds and a divalent halogenated arylene compound to polycondensation reaction in the presence of a transition metal catalyst (Patent Literatures 1 and 2). It has also been reported about a synthetic example of an acetylene-containing high molecular weight silicon compound (Non-Patent Literature 1).
However, the organopolysiloxane compound which is either a linear or a branched, and having at least one unit of the following formula (a) as a partial structure is limited to an organopolysiloxane compound where N=0 and M=0 to 20 in the following formula (a), and there is no reported example about an organopolysiloxane compound having a higher polymerization degree and having an ethynyl group at its polymer terminal.

Also, an organopolysiloxane compound having terminal ethynyl groups represented by the following formula (b) is limited only to an organopolysiloxane compound wherein N=0 and M=0 to 20 in the following formula (b), and it has not been reported about a method for preparing an organopolysiloxane compound having ethynyl groups at the polymer terminals with a higher polymerization degree.

For example, when an organopolysiloxane compound having an ethynyl group at its terminal is to be synthesized by an alkali equilibration, an alkali metal forms a metal acetylide such as C-M (M is an alkali metal) by substituting with H of the C—H bond at the acetylene portion, so that it is difficult to synthesize an organopolysiloxane compound having an ethynyl group at its terminal having a higher polymerization degree.
Also, a room temperature curable composition which cures to an elastomer state at a room temperature by contacting with a moisture in the air has conventionally been known various types of materials, and above all, a material of the type which cures by discharging an alcohol is preferably used for sealing, adhesion or coating of an electric and electronic devices, etc., due to its characteristics that there is no unpleasant smell and it does not corrode metals.
Representative examples of such a type may be mentioned those disclosed in Patent Literature 3, and a composition comprising an organopolysiloxane the terminal of which has been blocked by a hydroxyl group, an alkoxysilane and an organotitanium compound has been disclosed therein. Also, in Patent Literature 4, there is disclosed a composition comprising an organopolysiloxane the terminal of which has been blocked by an alkoxysilyl, an alkoxysilane and an alkoxytitanium. In Patent Literature 5, there is disclosed a composition comprising a linear organopolysiloxane having an alkoxysilyl-ethane group, an alkoxysilane and an alkoxytitanium. Further, in Patent Literature 6, there is disclosed a composition comprising an organopolysiloxane the terminal of which has been blocked by a hydroxyl group or an organopolysiloxane the terminal of which has been blocked by an alkoxy group, and an alkoxy-α-silyl ester compound.
These compositions gave good characteristics in storage stability and durability (water resistance and humidity resistance), but they were insufficient with regard to rapid curability.
An organosiloxane polymer having a reactive alkoxysilyl group at its terminal has conventionally been known. The terminal group of the organosiloxane polymer has previously been blocked by an alkoxysilyl group so that curability of the polymer difficulty change (lower) with a lapse of time, and a composition excellent in storage stability can be obtained. Also, workability (viscosity and thixotropic property) thereof can be optionally adjustable, and it reacts with a moisture in the air to form an elastomer by crosslinking, whereby excellent characteristics (hardness, tensile strength and elongation at break) can be also obtained.
However, a dealcoholation type room temperature curable organopolysiloxane composition comprising an organosiloxane polymer having such a reactive alkoxysilyl group at its terminal as a main agent (a base polymer) was insufficient in curability as compared to the other′ conventionally known curing types such as a deoximation type, a deacetylation type, a deacetone type, etc., since reactivity with a moisture in the air is low.
As a measure thereof, researches focused on a functional group (a bonding group) adjacent to the reactive alkoxy group have been promoted, and it has been reported that an α-alkoxysilylmethyl terminal group has particularly high reactivity with a moisture in the air (Patent Literature 7). However, curability thereof is yet insufficient, and there are defects that the adjacent functional group (bonding group) exerts bad effect to durability, and a restoring force of the cured product is low.